Java void visitor

PartitionFoos.java

class PartitionFoos {
  void doStuff(Collection<Foo> foos) {
    final List<Bar> bars = new ArrayList<>();
    final List<Baz> bazes = new ArrayList<>(); 
    for (Foo f : foos) {
      f.match(new Visitor<Void>() {

        @Override
        public Void caseBar(Bar b) {
          bars.add(b);
          return null;
        }

        @Override
        public Void caseBaz(Baz b) {
          bazes.add(b);
          return null;
        }
        
      });
    }
  }

}